Some optical projection systems can display multiple images for several observers to view simultaneously. For example, in some flight and combat simulators, distortionless images are displayed to observers to provide them with simulated practice environments. Different observers are seated close together at fixed locations and simultaneously view respectively different images. To prevent the different projected images from interfering with each other, separate viewing volumes can be provided for each observer. However, building separate viewing volumes for each observer can be an expensive undertaking.
Other optical projection systems have used beamsplitters to provide multiple images to multiple observers. In these systems, a lens-projector and beamsplitter combination is used, and images are simultaneously displayed on a non-spherical screen to spatially separated observers. Each observer is placed in a fixed position such that his or her eyes are placed at substantially the same reflected position as the projector lens to view a distortionless, bright, optically brilliant image. Moreover, each observer is able to view a discrete image, which is not viewable by other observers, on the projection screen. In essence, the image viewed by any one individual observer at the optimum position appears sufficiently bright in contrast to the image viewed by other observers to "wash out" the other image, thus rendering it unable to cause interference with the image being specifically viewed by the individual observer. To view a distortionless, optically brilliant image, each observer must be at a specified or exact position to view the desired discrete visual information.
The system just described, while effective in some instances, could be improved. For example, when the position of the system components are fixed, the location of the observer's eyes must be positioned at a particular location to observe an image of optimal quality. Since observers have different heights, an observer may have to adjust his or her body to place his or her eyes at the optically correct position. This can result in an inconvenient viewing experience for the observers.
Embodiments of the invention address these and other problems.